Merge branch '6.1.x'

Closes gh-13483

web/src/test/java/org/springframework/security/web/savedrequest/DefaultSavedRequestTests.java

@@ -122,4 +122,14 @@ public class DefaultSavedRequestTests {
 		assertThat(new URL(savedRequest.getRedirectUrl())).hasQuery("foo=bar&success");
 	}
 
+	// gh-13438
+	@Test
+	public void getRedirectUrlWhenQueryAlreadyHasSuccessThenDoesNotAdd() throws Exception {
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.setQueryString("foo=bar&success");
+		DefaultSavedRequest savedRequest = new DefaultSavedRequest(request, new MockPortResolver(8080, 8443),
+				"success");
+		assertThat(savedRequest.getRedirectUrl()).contains("foo=bar&success");
+	}
+
 }